1. Field of the Invention
This invention relates generally to light control circuits and more particularly to a lightweight light which can be mounted on a hat and a control circuit therefor which selectively controls the intensity of the light.
2. Description of the Prior Art
Lightweight battery powered lights have found many uses and are quite common. Some of these uses, however, require that the light maximize battery life to give an added measure of protection to the user. One such use is spelunking where helmet mounted head lamps are frequently used. It is crucial that battery life be extended as much as possible in spelunking since the availability of a light can become a life or death matter for the spelunker and since only a limited battery weight can be carried by the spelunker. In spelunking, the required level of intensity of the illumination provided by the head lamp varies widely since only minimal illumination is required to negotiate small passages whereas a bright light is required to probe heights and distances in large rooms and dome pits. Because of this wide range of intensity requirements, head lamps used for spelunking should have the capability of a wide range of intensities to satisfy the viewing requirements of the spelunker while at the same time minimizing power drain on the battery.
Numerous controls are available to selectively vary the illumination intensity of a lamp. Most of these controls are not concerned with battery life and thus impose significant power drain on the battery just to drive the control circuit to vary the illumination intensity of the light. These prior art control circuits also frequently reduced the voltage available to the light. Examples of such prior art control circuits are found in U.S. Pat. Nos. 3,800,136 and 3,821,600. As a result of these limitations, such prior art control circuits have not found applications in head lamps of the type normally used in spelunking.